Spring fastener with highly improved lever/angle pulling force

ABSTRACT

A spring fastener characterized by a structure having a cavity in which the rib of a first part, such as a plastic panel for example, like a pillar, may be engaged, and is also suitable to be engaged reversibly in a slot of second part, such as a metal sheet for example, like the frame of a car. The spring fastener comprises engagement springs having a peak, engagement regions and-side cuts in the vicinity of the peak, preferably within the engagement regions. The side-cuts, of preferably triangular shape, increase considerably the lever/angle pulling force (pulling force applied on the first part and away from the spring fastener, in order to separate the first part from a second part connected together with the spring fastener). It is highly preferable that the fastener comprises barbs with inwardly bent front ends, and that the engagement regions further have hindrance portions, the combination of which highly improves the balance of insertion to removal ratio.

RELATED APPLICATIONS

This application claims priority of provisional patent application 60/520/807, filed Nov. 17, 2003, which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

This invention relates to spring fasteners characterized by a structure having a cavity in which an extension or rib of a first part, such as a plastic panel for example, may be engaged, and they are also suitable to be engaged reversibly in a slot of second part, such as a metal sheet or the frame of a car for example. The invention also pertains an assembly of the first and the second part as connected to each other through the fastener, as well as vehicles comprising such assemblies.

BACKGROUND OF THE INVENTION

A number of fasteners have been used in the past for securing one object on another object, as for example, securing an article such as for example a plastic sheet on a metal or other rigid plastic sheet. However, the fasteners of the type, which are improved by the advances of the present invention, and being used presently, have a rather low ratio of insertion force to removal force. In other words, they require considerable force to be inserted into a slot in order to provide adequate removal resistance in order to be removed from the slot. This is ergonomically inferior performance, and the operators may suffer miscellaneous ailments, while productivity is also considerably undermined. In addition the fasteners of the present state in the art suffer from rather inferior Lever/Angle Pulling force.

Lever/Angle pulling force is defined as the force required to separate one part from another part connected with a fastener by pulling said parts apart, not straight away form each other, but sideways from each other, as will be described in more detail hereinbelow.

One of the major objectives of the present invention is to provide fasteners of considerably higher Lever/Angle pulling force than the fasteners of the present state in the art.

Recently, a fastener has been disclosed in U.S. Pat. No. 6,718,599 B2, which is incorporated herein by reference, characterized by ergonomically balanced removal to insertion force ratio. However, even in this case, the Lever/Angle pulling force is relatively low.

Examples of other state in the art fasteners are disclosed in U.S. Pat. No. 6,381,811 (Smith et al.), U.S. Pat. No. 6,353,981, U.S. Pat. No. 6,074,150 (Shinozaki et al.), U.S. Pat. No. 5,987,714 (Smith); U.S. Pat. No. 5,887,319 (Smith); U.S. Pat. No. 5,542,158 (Gronau et al.); U.S. Pat. No. 5,422,789 (Fisher et al.), U.S. Pat. No. 5,373,611 (Murata); U.S. Pat. No. 5,314,280 (Gagliardi); U.S. Pat. No. 5,095,592 (Doerfling); U.S. Pat. No. 4,701,984 (Wyckoff), U.S. Pat. No. 4,792,475 (Bien); U.S. Pat. No. 4,683,622 (Ohelke); U.S. Pat. No. 4,609,170 (Schnabl); U.S. Pat. No. 4,245,652 (Kelly et al.); U.S. Pat. No. 3,864,789 (Leitner); U.S. Pat. No. 3,673,643 (Kindell); U.S. Pat. No. 3,525,129 (Holton); U.S. Pat. No. 2,825,948 (Parkin); U.S. Pat. No. 2,607,971 (Bedford, Jr.); U.S. Pat. No. 2,542,883 (Tinnerman); U.S. Pat. No. 2,329,688 (Bedford, Jr.); U.S. Pat. No. 2,322,656 (Murphy), among others.

U.S. Pat. No. 5,919,019 (Fisher) provides fasteners which can only be permanently installed into a slot; they can only be inserted but not extracted without damage to parts of the fastener. The major engagement is performed by spring strips, while frictional portions of the fastener pass through the slot with at most slight compression, and immediately after the insertion of the fastener they are located in slightly spaced or barely contacting relation with the edges of the slot. They are only activated for engagement after the insertion of a bolt into a hole at the base plate. Thus, the profound effect of the increased removal to insertion ratio (explained in detail hereinbelow) is not recognized, mentioned, or implied. Thus, the intentionally provided distance of the frictional portions away from the edges of the slot by Fisher, during insertion and before use of the bolt, teaches actually away from the instant invention, which recognizes and takes full advantage of the increased removal to insertion ratio by an engagement region having a hindrance portion. As a matter of fact, if the engagement surfaces of the instant invention were located in slightly spaced or barely contacting relation with the edges of the slot, no engagement at all would take place upon insertion of the fastener of this invention into the slot.

U.S. Pat. No. 6,141,837 (Wisniewski) describes a spring fastener comprising bulbous and outwardly projecting portions, which assist in preventing withdrawal of the clip and associated molding from an aperture of a vehicle frame. However, “bulbous projections” are necessarily voluminous, take most of the space between the “reverse bents”, and unless they are manufactured within tight tolerances with regard to the thickness of the frame, the “base plates” do not sit on the frame (see also the Figures), rendering the structure unstable.

U.S. Pat. No. 6,203,240 B1 (Hironaka et al.), U.S. Pat. No. 5,129,768 (Hoyle et al.), U.S. Pat. No. 5,092,550 (Bettini), U.S. Pat. No. 4,981,310 (Belissaire), U.S. Pat. No. 4,712,341 (Harris, Jr. et al.), U.S. Pat No. 4,595,325 (Moran et al.), U.S. Pat. No. 4,431,355 (Junemann), U.S. Pat. No. 4,133,246 (Small), and U. S. Pat. No. 2,424,757 (F. Klump, Jr.) are directed to plastic or metal fasteners which are designed to be just inserted into the slot of a panel, but not extracted without damage to the fastener (if such extraction would be attempted from the front side; the side from which the fastener is inserted into the panel, since the back part of the panel is not reachable in the cases, wherein such types of fasteners are used).

None of the above disclosures of the present state in the art provide satisfactory Lever/Angle pulling force.

SUMMARY OF THE INVENTION

As aforementioned, this invention relates to spring fasteners characterized by a structure having a cavity in which the rib of a first part, such as a plastic panel for example, may be engaged, and they are also suitable to be engaged reversibly in a slot of second part, such as a metal sheet or the frame of a car for example. The invention also pertains an assembly of the first and the second part as connected to each other through the fastener, as well as vehicles comprising such assemblies. The spring fasteners of the present invention are characterized by a Lever/Angle pulling force, which is considerably higher than that characterizing spring fasteners of the present state in the art.

A very unexpected increase in Lever/Angle pulling force is attained by forming a side-cut section, especially at least partially bent outwardly, disposed in critical positions of the spring fastener, as will described in more detail hereinbelow.

Outwardly means away from the fastener.

More particularly, this invention pertains a spring fastener comprising a first side and a second side opposite the first side, the first side connected to the second side thereby forming a U-shaped structure having a cavity between the first side and the second side, a bottom portion wherein the first side and the second side are connected, and a top portion, the first side comprising a first spring, the first spring connected to the first side in the vicinity of the bottom portion, the second side comprising a second spring, the second spring connected to the second side in the vicinity of the bottom portion, each of the first and second engagement springs comprising a peak, a free end in the vicinity of the top portion, and an engagement region between the peak and the front end, at least one spring further having a side-cut section or notch, preferably in the vicinity the respective peak, the side-cut section or notch oriented substantially parallel to the peak. It is preferable, however, that each spring has two side-cut sections, one opposite to the other.

The side-cut sections or notches have an upper edge and a lower edge. It is highly preferable that at least one of the lower edges, and even more preferable that all lower edges are at least partially bent outwardly.

This invention further pertains an assembly comprising:

a spring fastener comprising a first side and a second side opposite the first side, the first side connected to the second side thereby forming a U-shaped structure having a cavity between the first side and the second side, a bottom portion wherein the first side and the second side are connected, and a top portion, the first side comprising a first spring, the first spring connected to the first side in the vicinity of the bottom portion, the second side comprising a second spring, the second spring connected to the second side in the vicinity of the bottom portion, each of the first and second engagement springs comprising a peak, a free end in the vicinity of the top portion, and an engagement region between the peak and the front end, at least one spring further having a side-cut section, preferably in the vicinity the respective peak, the side cut section oriented substantially parallel to the peak, and having an upper edge and a lower edge;

a first part comprising a rib inserted into the cavity of the spring fastener and engaged to the first and second barbs; and/or

a second part comprising a slot, the slot having a width and edges, the fastener being disposed in the slot in a manner that the edges of said slot are engaged to the engagement regions of the spring fastener.

In addition, this invention is related to a vehicle which comprises an assembly, the assembly comprising vehicle comprising an assembly, the assembly comprising:

a spring fastener comprising a first side and a second side opposite the first side, the first side connected to the second side thereby forming a U-shaped structure having a cavity between the first side and the second side, a bottom portion wherein the first side and the second side are connected, and a top portion, the first side comprising a first spring, the first spring connected to the first side in the vicinity of the bottom portion, the second side comprising a second spring, the second spring connected to the second side in the vicinity of the bottom portion, each of the first and second engagement springs comprising a peak, a free end in the vicinity of the top portion, and an engagement region between the peak and the front end, at least one spring further having a side-cut section, preferably in the vicinity the respective peak, the side cut section oriented substantially parallel to the peak, and having an upper edge and a lower edge;

a first part comprising a rib inserted into the cavity of the spring fastener and engaged to the first and second barbs; and

a second part comprising a slot, the slot having a width and edges, the fastener being disposed in the slot in a manner that the edges of said slot are engaged to the engagement regions of the spring fastener.

It is preferable that the fastener comprises hindrance portion within the engagement region, and more preferable that the side-cut section is disposed within the engagement region. It is further highly preferable that the side-cut section has a triangular shape.

The spring fastener of the present invention may further comprise a recess within the engagement region, in the vicinity of the top end.

The hindrance portion may have any suitable structure, which hinders to a desired degree the removal of the spring fastener from the slot described above. It is preferable, however, that said hindrance portion comprises one structure selected from ripple, side rib, upward solid bent extension parallel to the peak and the optional recess, knurled region, bent teeth, each having a depth, a bump or bulbous formation, and a combination thereof.

The presence of a single ripple in the vicinity of the peak is more preferable according to this invention, and it is even more preferable that the ripple has a back side with a curvature of a gradually decreasing slope. Preferably, the gradually decreasing slope has the shape of an arc in the range of 50–70 degrees with a radius in the range of 0.03–0.05 mm.

More details regarding preferred configurations of engagement regions are described in Non-provisional patent application Ser. No. 10/164,963, filed Jun. 7, 2002, and its respective Patent Application Publication US 2002/0194710 A1, Pub. Date Dec. 26, 2002, both of which are incorporated herein by reference.

It is further preferable that the spring fastener of this invention further comprises first barbs and second barbs being cut portions of the respective first and second side of the spring fastener, originating from the vicinity of the top portion of said spring fastener and directed toward the bottom portion the spring fastener, the first barbs and the second barbs comprising respective first back sections and first front sections, the first sections being bent portions of the first back sections, and second back sections and second front sections, the second front sections being bent portions of the second back sections.

The barbs are preferably selected from a group consisting essentially of:

-   -   first barbs being outer barbs and second barbs being inner         barbs;     -   first barbs being outside outer barbs and second barbs being         inside outer barbs; and     -   first barbs being inner barbs and second barbs being inner         barbs.

It is preferable that the barbs which are cut from their respective side, are flexible, and bent in the vicinity of their respective front end as described for example in U.S. Pat. No. 6,279,207 B1, which is incorporated herein by reference, and more particularly in FIG. 1A of said patent, with an angle of bent in the range of 5–25 degrees.

The barbs are considered to be flexible if they do not cause the width W3 (FIG. 1B) to increase more than 30%, preferably 20%, and more preferably 10%, when the rib 46 is inserted into the cavity 19 of the fastener 10 (FIG. 4A), and provided that the first object 46 is adequately hard to hinder the barbs 36 from substantially digging into it.

Regarding the outside outer barbs, it is preferable that their front points are at a distance from the second side smaller than the thickness of the material from which the spring fastener was made. This is to avoid interconnection of the fasteners, when said fasteners are stored in bulk.

The barbs may have variable width along their length, or they may have substantially the same width along their length. Further, the front points of the barbs may be toothed.

More details regarding our preferred bent barbs are also described in U.S. Pat. Nos. 6,279,207 B1 and 6,691,380 B2, both of which are incorporated herein by reference.

The spring fastener of the instant invention may further comprise a molded elastic body at least under the top portion of said spring fastener for sealing purposes. Such arrangements are disclosed in U.S. Pat. No. 6,353,981 B1, which is incorporated herein by reference. Other sealing arrangements are also included in the instant invention, as described for example in U.S. Pat. No. 6,527,471 B2, which is also incorporated herein by reference.

In another embodiment, the spring fastener of the instant invention may further comprise:

an elastic body comprised of at least a gasket, the gasket extending away from the cavity in the vicinity of the top portion of the fastener and enclosing at least partially the cavity; and

a casing surrounding at least partially the spring fastener under the top portion, except at least the engagement section of each engagement spring, the casing also at least partially surrounding the cavity and such portion of the elastic body which at least partially encloses the cavity;

wherein the casing has lower ultimate elongation, higher Shore hardness, and higher shear strength than the elastic body. Thus, preferably the casing is substantially non-elastic.

Such arrangements are disclosed in U.S. Pat. Nos. 6,381,811 B2, 6,497,011 B2, 6,527,471 B2, and 6,648,547 B2, all of which is incorporated herein by reference.

According to the present invention, any embodiments of fasteners described above and their equivalents may be used in any assembly in which the first part and/or the second part are connected with the fastener, as well as in any vehicle comprising such an assembly or such a fastener or its equivalents.

DESCRIPTION OF THE DRAWING

The reader's understanding of practical implementation of preferred embodiments of the invention will be enhanced by reference to the following detailed description taken in conjunction with perusal of the drawing figures, wherein:

FIG. 1 illustrates a perspective view of a spring fastener according to a preferred embodiment of the present invention, wherein the engagement regions of the first and second springs have side-cut sections or notches in the vicinity of the bent.

FIG. 1A 1 illustrates a perspective view of a spring fastener according to another preferred embodiment of the present invention, wherein the hindrance portion comprises a single-sided ripple and bent barbs, and the engagement regions of the first and second springs have side-cut sections or notches in the vicinity of the bent.

FIG. 1B shows a side view of the spring fastener of FIG. 1A.

FIG. 1C illustrates a perspective view of a spring fastener according to another preferred embodiment of the present invention, wherein the lower edges of the side-cut sections or notches are at least partially bent outwardly.

FIG. 2 illustrates a perspective view of a spring fastener according to another preferred embodiment of the present invention, wherein the hindrance portion comprises one two-sided ripple and bent barbs, and the engagement regions of the first and second springs have side-cut sections or notches in the vicinity of the bent.

FIG. 3A illustrates side view of an engagement spring, wherein the hindrance portion comprises a single-sided ripple, and the engagement regions have side-cut sections or notches in the vicinity of the bent.

FIG. 3B illustrates a side view of an engagement spring, wherein the hindrance portion comprises one two-sided ripple, and the engagement regions have side-cut sections or notches in the vicinity of the bent.

FIG. 3C illustrates a side view of an engagement spring, wherein the hindrance portion comprises two two-sided ripples, and the engagement regions have side-cut sections or notches in the vicinity of the bent.

FIG. 3D illustrates a side view slice of an engagement spring, wherein the hindrance portion comprises three two-sided ripples, and the engagement regions have side-cut sections or notches in the vicinity of the bent.

FIG. 4 illustrates two parts, which can be connected with the fastener according to the present invention.

FIG. 4A illustrates the side view of the fastener of FIG. 1A and a cross sectional slice of the rib of a first part, such as a panel or an automotive pillar, for example, inserted into the cavity of the fastener.

FIG. 4B illustrates the same elements shown in FIG. 4A after insertion of the fastener into the slot of a second part, such as the frame of an automobile for example.

FIG. 4C illustrates a partial cross section of the second part of FIG. 4B and the edges of the slot in relation with the engagement regions of the engagement springs of the fastener.

FIG. 5 illustrates a detailed diagram of a ripple in the hindrance portion according to preferred embodiments of the instant invention.

FIG. 5A illustrates a detailed diagram of a single-sided ripple having a back side in the form of a curvature in the hindrance portion according to a highly preferred embodiment of the instant invention.

FIG. 6 illustrates a stamped fastener before final formation according to another embodiment of the present invention, wherein the fastener comprises outer and inner barbs, as well as relief portions in the vicinity of the bottom of the fastener.

FIG. 6A illustrates a side view of the fastener of FIG. 6 after final formation.

FIG. 7 illustrates a stamped fastener before final formation according to another embodiment of the present invention, wherein the fastener comprises outside outer barbs on the first side and inside outer barbs on the second side.

FIG. 8 illustrates a stamped fastener before final formation according to another embodiment of the present invention, wherein the fastener comprises only inner barbs.

FIG. 9 illustrates a stamped fastener before final formation according to another embodiment of the present invention, wherein the fastener comprises upper and lower outer and inner barbs.

FIG. 10 illustrates a stamped fastener before final formation according to another embodiment of the present invention, wherein the fastener comprises two engagement springs per side of the fastener, and only one upper and one lower barb per side.

FIG. 11 illustrates a stamped fastener before final formation according to another embodiment of the present invention, wherein the barbs have uniform width along their length.

FIG. 12 illustrates a stamped fastener before final formation according to another embodiment of the present invention, wherein the barbs have uniform width along their length, and they are toothed at their front ends.

FIG. 13 illustrates a cross-sectional slice of the middle portion of a spring fastener, according to another embodiment of the instant invention, wherein a molded elastic body 54 is disposed at least under the top portion of said spring fastener.

FIG. 14 is a perspective view of a fastener, according to still another embodiment of the instant invention, wherein the lower portion of the fastener is covered by a casing, while an elastic body is disposed in the vicinity of the top portion and encloses the cavity, at least partially.

DETAILED DESCRIPTION OF THE INVENTION

As aforementioned, this invention relates to spring fasteners characterized by a structure having a cavity in which the rib of a first part, such as a plastic panel for example, like a pillar for example, may be engaged, and they are also suitable to be engaged reversibly in a slot of second part, such as a metal sheet for example, like the frame of a car for example. The invention also pertains an assembly of the first part connected to the fastener, the first and the second part connected to each other through the fastener, as well as vehicles comprising such assemblies.

More particularly, as better shown in FIGS. 1, 1A and 1B, the invention pertains a spring fastener 10 comprising a first side 12 and a second side 14 opposite the first side 12. The first side 12 is connected to the second side 14 forming a U-shaped structure which has a cavity 19 between the first side 12 and the second side 14. The fastener 10 also has a bottom portion 16, wherein the first side 12 and the second side 14 are connected. It further has a top portion 18 a and 18 b (collectively 18).

In all cases, numerals referring to the first side 12 contain the letter “a”, while numerals referring the second side 14 contain the letter “b”. The same numerals without the letters “a” or “b”, refer collectively to the respective elements of both sides.

The first side 12 comprises a first engagement spring 20 a, which is connected to the first side 12 in the vicinity of the bottom portion 16.

The second side 14 comprises a second engagement spring 20 b, which is connected to the second side 14, also in the vicinity of the bottom portion.

Each of the first and second engagement springs 20 a and 20 b may preferably, but not necessarily, have a first and second recess, 24 a and 24 b, respectively, as shown in FIGS. 1A and 1B, and a first and second free end, 22 a and 22 b, respectively, in the vicinity of the top portion 18 (18 a and 18 b, respectively). Each spring also comprises a first and a second peak, 26 a and 26 b, respectively, and a first and second engagement region, 28 a and 28 b, respectively.

Preferably, within the engagement region, and more preferably in the vicinity of the peaks 26, there are side-cut sections 8 a and 8 b on the spring sides consisting of side-cuts 8a and 8b (collectively 8), respectively, preferably of triangular shape, which render the lever/angle pulling force considerably higher than it would have been in their absence. Each one of the side-cuts or notches 8 has an upper edge 7 (7 a and 7 b), and a lower edge 9 (9 a and 9 b). It is highly preferable that the lower edges 9 (9 a and 9 b) are at least partially bent outwardly, as better illustrated in FIG. 1C. It is evident that the invention includes the case that only one side-cut section may be present.

As aforementioned, lever/angle pulling force is defined as the force required to separate one part from another part connected with a fastener by pulling said parts apart, not straight away form each other, but sideways from each other.

It is highly preferable also, that the engagement regions 28, further comprise a first and second hindrance portion, 29 a and 29 b, respectively, between the bents 26 and the front ends 22.

The hindrance portions provide increased removal force, when the fastener 10 is pulled by a rib or extension 46 (FIG. 4B) of a first part 44 (FIG. 4) engaged to the first and second barbs, 36 a and 36 b, respectively, after the fastener 10 has been inserted into a slot 50 of a second part 48 (FIG. 4), the slot 50 having a slot width W2 (FIGS. 4 and 4C) and edges 51 (FIG. 4C) on which edges the engagement regions 28 a and 28 b are engaged. The removal force is measured by pulling rib 46 of the first part 44 straight away from the second part 48 in the vicinity of point F1.

The increased removal force is due to the hindrance portions 29 a and 29 b (FIG. 4C), which in this particular case comprise single ripples with only back sides 34, as it will be explained at a later point in more detail. According to this invention, the engagement portions 28 a and 28 b and the hindrance regions 29 a and 29 b are required to be such that the fastener 10 can be extracted from the slot 50 when pulled by the rib 46 without damage to said fastener 10, and with a higher force than a force required in the absence of the hindrance portions 29 a and 29 b.

The lever/angle pulling force is measured by pulling the first part 44 apart from the second part 48, not straight away, but sideways from each other, that is for example by pulling the first part 44 from a point F2 away from the rib 46, such as the edge 45 for example of the first part 44, such as an automotive pillar for example.

In different applications, the exact position of point F2 may be different, as well as the required increase in lever/angle force by the use of the side-cut sections.

The first side 12 also comprises first barbs 36 a, which in the case shown in FIGS. 1A and 1B are outer barbs, since they are disposed in an outer portion of the first side 12. The barbs 36 a have first front ends 38 a. In the particular cases of FIGS. 1A and 1B, the first barbs 36 a are bent inwardly in the vicinity of the front ends 38 a, according to a highly preferred embodiment of the instant invention.

The second side 14 comprises second barbs 36 b, which in the case of FIGS. 1A and 1B are inner barbs, since they are disposed in an inner portion of the second side 14. The second barbs have second front ends 38 b. In this particular case of FIGS. 1A and 1B the second barbs 36 b are also bent inwardly in the vicinity of the front ends 38 b, according to a highly preferred embodiment of the instant invention.

In the case of FIG. 1, the barbs 36 a and 36 b are straight.

This invention further pertains an assembly 11, as better shown in FIG. 4B, comprising a spring fastener as described above or in the embodiments and their equivalents presented hereinbelow, and a first part 44 (FIG. 4) comprising a rib 46 (FIG. 4A) inserted into the cavity 19 of the spring fastener 10 and engaged to the first and second barbs 36 a and 36 b.

Further, this invention further pertains an assembly 1, as better shown in FIG. 4B, comprising a spring fastener as described above or in the embodiments presented hereinbelow; a first part 44 (FIG. 4) comprising a rib 46 (FIG. 4A) inserted into the cavity 19 of the spring fastener 10 and engaged to the first and second barbs 36 a and 36 b; and a second part 48 (FIGS. 4 and 4B) comprising a slot 50, which slot 50 has a width W2 and edges 51 (FIG. 4C), so that the edges 51 of said slot are engaged to the engagement regions 28 a and 28 b of the spring fastener 10. In this case also, the requirement exists that by pulling the rib 46, the fastener 10 is extracted from the slot 50 without damage to the fastener 10, and with a higher force than a force required in the absence of the hindrance portions 29 a and 29 b.

In addition, this invention is related to a vehicle which comprises an assembly 11, as described above.

In operation of the above embodiments, the spring fastener 10 of the present invention is intended to connect a first part, such as a panel 44 for example, which panel may have a rib 46, with a second part, such as a frame 48 of a car for example, having a slot 50, as illustrated in FIG. 4.

The rib 46 of the panel 44 is preferably first inserted into the cavity 19 of the fastener 10 (see FIG. 4A), where, it is secured by barbs 36 a and 36 b. Then, the fastener 10, which has been secured on the extension 46 of the panel 44, is inserted into the slot 50 of the frame 48, as better shown in FIG. 4B. However the sequence inserting the fastener may be the opposite.

In this manner, the first part, exemplified by panel 44, has been connected on the second part, exemplified by frame 48, through the fastener 10 of the instant invention.

In most practical applications, the length Le (see FIG. 4A) of the engagement regions 28 is not higher than 2–4 mm, while the thickness T_(f) of the frame 48 (see FIG. 4B) may vary in most occasions in the range of 0.5 to 2 mm. This fact makes it rather difficult to form large hindrance portions. Thus, The “bulbous projections” suggested by U.S. Pat. No. 6,141,837 (Wisniewski) are necessarily too bulky and voluminous, take most of the space between the “reverse bents” (engagement regions between the peak and the recess in the case of the instant invention), and unless they are manufactured within tight tolerances with regard to the thickness of the frame (which in practice may vary considerably), the “base plates” (top portions in the case of the present invention) do not sit on the frame (see also Wisniewski's Figures), rendering the structure considerably unstable.

According to this invention, and particularly for ergonomic purposes combined with practical aspects, it is highly preferable that the force to insert the rib of the first part into the cavity of the spring fastener should be less than 40 lbs, preferably less than 15 lbs, and even more preferably less that 10 lbs; the force to insert the spring fastener into the slot should be less that 30 lbs, preferably less than 15 lbs, and even more preferably less than 10 lbs; and the force to extract the spring fastener from the slot should be in the range of 30–100 lbs, and preferably in the range of 50–70 lbs.

It was unexpectedly found by the inventors that in order to achieve the above results, the hindrance portions should comprise rather minute elements, and not the huge structural components disclosed in the art. Such huge structural components render respective fasteners to be irreversibly inserted into slots. Any attempt to extract these fasteners from the side of the panel that they were inserted would result in destruction of the fasteners.

According to this invention, the hindrance portions 29 a and 29 b may comprise minute elements, such as ripples, upward solid bent extensions parallel to the peaks and the recesses, knurled regions, bent teeth, each having a depth, the depth of which does not exceed preferably 0.2 mm, and more preferably 0.1 mm. Any person of ordinary skill in the art would not expect that elements having such minute depths would have such great impact in force balances as the aforementioned ones.

The depth for any element is substantially defined in the same manner as defined at a later point for the ripples.

Although this invention includes any structure which satisfies the claims, such as for example upward solid bent extensions parallel to the peaks and the recesses, knurled regions, bent teeth, as described in at least one of the provisional patent application 60/301,364, filed Jun. 25, 2001, 60/327,814, filed Oct. 9, 2001, and 60/353,515, filed Feb. 1, 2002, U.S. Pat. No. 6,718,599 B2, and U.S. Pat. No. 6,745,440 B2, all of which are incorporated herein by reference, and as long as their depth does not exceed 0.2 mm, the most preferable configuration is one that comprises at most three ripples having a preferable depth not exceeding 0.2 mm, and more preferably not exceeding 0.1 mm. It is more preferable that the hindrance portion comprises not more than two ripples, and even more preferable one ripple. Structures with one to three two-sided ripples 30 are shown in FIGS. 3B to 3D, respectively.

FIG. 2 illustrates a spring fastener 10 according to this invention, wherein the hindrance portion 29 comprises one two-sided ripple 30 and bent barbs 36.

The most efficient and effective case, however, according to this invention, is the use of only one single-sided ripple 30, as shown for example in FIGS. 1A and 3A.

The operation of these embodiments is substantially the same as the operation of the previous embodiments.

It is preferable that each ripple 30 is in the form of a depression, as better shown in FIG. 5. The depression has a deepest part Z, a front side 32, a back side 34, and a width W1. The hindrance portion 29 has a surface E, and the depth D of each ripple 30 is defined as the distance between the surface E of the hindrance portion 29 and the deepest part Z of the respective ripple 30.

For better performance, the ripple width is larger than the depth of the ripple, and preferably the ripple width is at least twice the size of the depth of the ripple. The ripple width is preferably in the range of 0.1 to 0.5 mm and the ripple depth is in the range of 0.01 to 0.1 mm, as aforementioned.

In a preferred embodiment, the back side 34 of the ripple 30 is substantially linear and has a slope S in the range of 15 to 30 degrees with regard to the general plane of the surface E of the hindrance portion 29, and it is also preferable that the front side 32 has a higher slope than the back side. The slope of the front side is measured in the same manner as the slope of the back side. Thus, if the front side 32 is substantially perpendicular to the surface E, the slope is substantially 0 degrees, while if the front side 32 is substantially parallel to the plane of surface E and the continuation of the deepest part Z, it is substantially 90 degrees.

It is, however, highly preferable that the back side 34 has the form of a curvature with a gradually decreasing slope. For example, the gradually decreasing slope of back side 34 may have the shape of an arc corresponding to an angle A1, preferably in the range of 50–70 degrees, with a radius R, preferably in the range of 0.03–0.05 mm., as better shown in FIG. 5A.

This configuration is of extreme importance in most occasions, because during vibrations, the edges 51 of the slot 50 (FIG. 4C) slide smoothly on the engagement regions 28 as well as the hindrance portions 29 during operation, and when they reach the back sides 34 of the single-sided ripples 30 (FIG. 5A), they continue sliding smoothly finding increasingly higher resistance in a continuous manner, which eliminates any rattling noises. Such rattling noises would be present in a case that the edges 51 would hit abrupt obstacles or would suddenly jump down, even without hitting such obstacles.

The barbs are preferably selected from a group consisting essentially of:

-   -   first barbs 36 a being outer barbs, and second barbs 36 b being         inner barbs, as better shown in FIG. 6 (blank before forming)         and 6A (side view);     -   first barbs 36 a being outside outer barbs, and second barbs 36         b being inside outer barbs, as better shown in FIG. 7 (blank         before forming); and     -   first barbs 36 a being inner barbs, and second barbs 36 b being         inner barbs, as better shown in FIG. 8 (blank before forming).

In operation, the barbs engage on the rib 46 of the first part 44, and when an adequate pulling force is applied on the firs part 44, the fastener remains on said first part 44, but is extracted from the slot 50.

The spring fastener 10 may also comprise relief openings 42 a and 42 b in the vicinity of the bottom 16 of the spring fastener 10, as better shown in FIG. 6 (blank before forming). These relief openings facilitate the insertion of the fastener into the slot 50.

The spring fastener 10 may further comprise additional lower barbs 40 a and 40 b pointing inwardly and originating form the vicinity of the bottom portion 16 of the first side and the second side, respectively, of the fastener 10, as better shown in FIG. 9 (blank before forming).

In another embodiment, better illustrated in FIG. 10 (blank before forming), the first side of the spring fastener 10 has only one upper barb 36 a and one lower barb 40 a, while the second side also has also only one upper barb 36 b and only one lower barb 40 b, in a manner that the upper barb of one side faces the lower barb of the other side and vice versa.

The barbs 36 may have variable width along their length, as illustrated in for example in FIGS. 6–10, or they may have substantially the same width along their length as better shown in FIG. 11. Further, the front points of the barbs 36 may be toothed, as illustrated in FIG. 12.

Regarding outside outer barbs 36, it is preferable that their front points 38 are at a distance C from the second side 14 smaller than the thickness T of the material from which the spring fastener 10 is made, as better shown in FIG. 1B. This is to avoid interconnection of the fasteners, when said fasteners are stored in bulk.

It is preferable that the barbs are cut from their respective side, are flexible, and bent in the vicinity of their respective front end as described for example in U.S. Pat. No. 6,279,207 B1, which is incorporated herein by reference, and more particularly in FIG. 1A of said patent, with an angle of bent in the range of 5–25 degrees.

It is also preferable that the fastener 10 has a width W3 (FIG. 1B) in the vicinity of the top portion 18 of the fastener 10, which is at least 60%, and more preferably at least 70%, as wide as the slot width W2 (FIG. 4C). Thus, it is preferable that the whole fastener complies with this requirement, or at least a portion in the vicinity of the top. This is to avoid reversal of the direction and failure of the barbs 36, when and if the rib 46 is forcefully pulled away from the second part 48 (FIG. 4B).

With respect to the engagement regions 28, it is preferable that these regions are at least partially wider than the rest of the respective engagement springs 20 (see for example FIG. 6).

The more barbs are present, or the more bent their front points are, the stronger the engagement of the rib 46 in the cavity 19. However, in many occasions it is desirable that this engagement is not so strong so as to destroy the integrity of the fastener or the rib, when an adequate force is applied to separate the fastener 10 from the rib 46.

The spring fasteners 10 of the instant invention may have two engagement springs 20 at the edges of each side instead of one engagement spring 20 in substantially the middle portion of each side (see for Example FIG. 10).

The spring fastener 10 of the instant invention may further comprise a molded elastic body 54 at least under the top portion 18 of said spring fastener 10, as better shown in FIG. 13. Such arrangements are disclosed in U.S. Pat. No. 6,353,981 B1, which is incorporated herein by reference.

The operation of this embodiment is similar to the operation of the previously described embodiments with the difference that the elastic body provides moderate sealing properties to the fastener when the fastener is inserted into the slot.

In another embodiment, the spring fastener of the instant invention may further comprise:

an elastic body 54 comprised of at least a gasket 56, the gasket 56 extending away from the closed cavity 19 in the vicinity of the top portion 18 of the fastener 10 and enclosing at least partially the cavity 19; and

a casing 58 surrounding at least partially the spring fastener under the top portion 18, except at least the engagement region 28 of each engagement spring 20, the casing 58 also at least partially surrounding the cavity 19 and such portion of the elastic body 54 which at least partially encloses the cavity;

wherein the casing 58 has lower ultimate elongation, higher Shore hardness, and higher shear strength than the elastic body 54;

as better shown in FIG. 14.

The presence of lips 60 improves considerably the sealing properties of the elastic body.

Such arrangements are also disclosed in U.S. Pat. No. 6,381,811 B2, which is incorporated herein by reference.

The operation of this embodiment is similar to the operation of the previously described embodiments with the difference that the combination of the elastic body 54 with the casing 58 provide outstanding sealing properties to the fastener 10 when the fastener 10 is inserted into the slot 50, and the casing itself facilitates the insertion of the fastener 10 into the slot 50.

According to the present invention, any embodiments of fasteners described above and their equivalents may be used in any assembly in which the first part and the second part are connected with the fastener, as well as in any vehicle comprising such an assembly or such a fastener or its equivalents. 

1. A spring fastener comprising a first side and a second side opposite the first side, the first side connected to the second side thereby forming a U-shaped structure having a cavity between the first side and the second side, a bottom portion wherein the first side and the second side are connected, and a top portion, the first side comprising a first engagement spring, the first engagement spring connected to the first side in the vicinity of the bottom portion, the second side comprising a second engagement spring, the second engagement spring connected to the second side in the vicinity of the bottom portion, each of the first and second engagement springs comprising a peak, a free end, and an engagement region between the peak and the free end, at least one engagement spring having two spring sides and a side-cut on each spring side, the side-cuts being across each other, thus forming a side-cut section aligned to be substantially parallel to the peak, each side-cut including an upper edge and a lower edge connecting with the respective spring side of the engagement spring.
 2. A spring fastener as defined in claim 1, further comprising a hindrance portion within the engagement region.
 3. A spring fastener as defined in claim 2, wherein the hindrance portion comprises one structure selected from ripple, side rib, upward solid bent extension parallel to the peak, knurled region, bent teeth, each having a depth, a bump, and a combination thereof.
 4. A spring fastener as defined in claim 3, wherein the engagement region comprises a ripple in the vicinity of the peak.
 5. A spring fastener as defined in claim 4, wherein the ripple has a back side with a curvature of a gradually decreasing slope.
 6. A spring fastener as defined in claim 5, wherein the gradually decreasing slope has the shape of an arc in the range of 50–70 degrees with a radius in the range of 0.03–0.05 mm.
 7. A spring fastener as defined in claim 2, further comprising first barbs and second barbs being cut portions of the respective first and second side of the spring fastener.
 8. A spring fastener as defined in claim 2, wherein the hindrance portion comprises: a single-sided ripple with a back side in the vicinity of the peak; and inside substantially upper barbs on both first and second sides of the fastener.
 9. A spring fastener as defined in claim 8, wherein the back side of the single ripple has a gradually decreasing slope.
 10. A spring fastener as defined in claim 1, wherein the side-cut section is disposed in the vicinity of the respective peak.
 11. A spring fastener as defined in claim 10, wherein the lower edge is at least partially bent outwardly.
 12. A spring fastener as defined in claim 11, further comprising a recess on at least one of: the first spring and the second spring.
 13. A spring fastener as defined in claim 12, further comprising first barbs and second barbs being cut portions of the respective first and second side of the spring fastener.
 14. A spring fastener as defined in claim 11, wherein the engagement region comprises one structure selected from ripple, side rib, upward solid bent extension parallel to the peak, knurled region, bent teeth, each having a depth, a bump, and a combination thereof.
 15. A spring fastener as defined in claim 14, wherein the engagement region comprises a ripple in the vicinity of the peak.
 16. A spring fastener as defined in claim 15, wherein the ripple has a back side with a curvature of a gradually decreasing slope.
 17. A spring fastener as defined in claim 16, wherein the gradually decreasing slope has the shape of an arc in the range of 50–70 degrees with a radius in the range of 0.03–0.05 mm.
 18. A spring fastener as defined in claim 14, further comprising first barbs and second barbs being cut portions of the respective first and second side of the spring fastener.
 19. A spring fastener as defined in claim 15, further comprising first barbs and second barbs being cut portions of the respective first and second side of the spring fastener.
 20. A spring fastener as defined in claim 16, further comprising first barbs and second barbs being cut portions of the respective first and second side of the spring fastener.
 21. A spring fastener as defined in claim 17, further comprising first barbs and second barbs being cut portions of the respective first and second side of the spring fastener.
 22. A spring fastener as defined in claim 11, further comprising first barbs and second barbs being cut portions of the respective first and second side of the spring fastener.
 23. A spring fastener as defined in claim 11, further comprising an elastic body molded at least under the lower side of the head of the fastener.
 24. A spring fastener as defined in claim 11, further comprising: a casing surrounding at least partially the lower section of the U-shaped structure, except at least the free end of each spring, the casing enclosing the cavity within the first side and the second side of said U-shaped structure; and an elastic body comprised of at least a gasket, the gasket extending away from the closed cavity in the vicinity of the top of the U-shaped structure; wherein the casing is substantially non-elastic.
 25. A spring fastener as defined in claim 10, further comprising a recess on at least one of: the first spring and the second spring.
 26. A spring fastener as defined in claim 10, wherein the engagement region comprises one structure selected from ripple, side rib, upward solid bent extension parallel to the peak, knurled region, bent teeth, each having a depth, a bump, and a combination thereof.
 27. A spring fastener as defined in claim 26, wherein the engagement region comprises a ripple in the vicinity of the peak.
 28. A spring fastener as defined in claim 27, wherein the ripple has a back side with a curvature of a gradually decreasing slope.
 29. A spring fastener as defined in claim 28, wherein the gradually decreasing slope has the shape of an arc in the range of 50–70 degrees with a radius in the range of 0.03–0.05 mm.
 30. A spring fastener as defined in claim 10, further comprising first barbs and second barbs being cut portions of the respective first and second side of the spring fastener.
 31. A spring fastener as defined in claim 1, wherein at least one of the side-cuts has a triangular shape.
 32. A spring fastener as defined in claim 1, wherein the lower edge is at least partially bent outwardly.
 33. A spring fastener as defined in claim 1, further comprising a recess on at least one of: the first spring and the second spring.
 34. A spring fastener as defined in claim 1, further comprising first barbs and second barbs being cut portions of the respective first and second side of the spring fastener.
 35. A spring fastener as defined in claim 1, further comprising an elastic body molded at least under the lower side of the head of the fastener.
 36. A spring fastener as defined in claim 1, further comprising: a casing surrounding at least partially the lower section of the U-shaped structure, except at least the free end of each spring, the casing enclosing the cavity within the first side and the second side of said U-shaped structure; and an elastic body comprised of at least a gasket, the gasket extending away from the closed cavity in the vicinity of the top of the U-shaped structure; wherein the casing is substantially non-elastic.
 37. A vehicle comprising parts connected with a spring fastener, the spring fastener comprising a first side and a second side opposite the first side, the first side connected to the second side thereby forming a U-shaped structure having a cavity between the first side and the second side, a bottom portion wherein the first side and the second side are connected, and a top portion, the first side comprising a first engagement spring, the first engagement spring connected to the first side in the vicinity of the bottom portion, the second side comprising a second engagement spring, the second engagement spring connected to the second side in the vicinity of the bottom portion, each of the first and second engagement springs comprising a peak, a free end, and an engagement region between the peak and the free end, at least one engagement spring having two spring sides and a side-cut on each spring side, the side-cuts being across each other, thus forming a side-cut section aligned to be substantially parallel to the peak, each side-cut including an upper edge and a lower edge connecting with the respective side of the engagement spring.
 38. A vehicle as defined in claim 37, wherein the spring fastener further comprises a hindrance portion between the peak and the free end.
 39. A vehicle as defined in claim 38, wherein the hindrance portion of the fastener further comprises one structure selected from ripple, side rib, upward solid bent extension parallel to the peak and the recess, knurled region, bent teeth, each having a depth, a bump, and a combination thereof.
 40. A vehicle as defined in claim 39, wherein the hindrance portion of the fastener further comprises a ripple in the vicinity of the peak.
 41. A vehicle as defined in claim 40, wherein the ripple comprises a back side with a curvature of a gradually decreasing slope.
 42. A vehicle as defined in claim 41, wherein the gradually decreasing slope has the shape of an arc in the range of 50–70 degrees with a radius in the range of 0.03–0.05 mm.
 43. A vehicle as defined in claim 38, wherein the fastener further comprising first barbs and second barbs being cut portions of the respective first and second side of the spring fastener.
 44. A vehicle as defined in claim 38, wherein the hindrance portion of the fastener comprises: a single-sided ripple with a back side in the vicinity of the peak; and inside substantially upper barbs on both first and second sides of the fastener.
 45. A vehicle as defined in claim 44, wherein the back side of the single ripple has a gradually decreasing slope.
 46. A vehicle as defined in claim 37, wherein the side-cut section of the spring fastener is disposed within the engagement region.
 47. A vehicle as defined in claim 46, wherein the lower edge of the side-cuts of the at least one engagement spring are at least partially bent outwardly.
 48. A vehicle as defined in claim 47, wherein the spring fastener further comprises a recess on at least one of: the first engagement spring and the second engagement spring.
 49. A vehicle as defined in claim 48, wherein the fastener further comprising first barbs and second barbs being cut portions of the respective first and second side of the spring fastener.
 50. A vehicle as defined in claim 47, wherein the hindrance portion of the fastener further comprises one structure selected from ripple, side rib, upward solid bent extension parallel to the peak and the recess, knurled region, bent teeth, each having a depth, a bump, and a combination thereof.
 51. A vehicle as defined in claim 50, wherein the hindrance portion of the fastener further comprises a ripple in the vicinity of the peak.
 52. A vehicle as defined in claim 51, wherein the ripple comprises a back side with a curvature of a gradually decreasing slope.
 53. A vehicle as defined in claim 52, wherein the gradually decreasing slope has the shape of an arc in the range of 50–70 degrees with a radius in the range of 0.03–0.05 mm.
 54. A vehicle as defined in claim 50, wherein the fastener further comprising first barbs and second barbs being cut portions of the respective first and second side of the spring fastener.
 55. A vehicle as defined in claim 51, wherein the fastener further comprising first barbs and second barbs being cut portions of the respective first and second side of the spring fastener.
 56. A vehicle as defined in claim 52, wherein the fastener further comprising first barbs and second barbs being cut portions of the respective first and second side of the spring fastener.
 57. A vehicle as defined in claim 53, wherein the fastener further comprising first barbs and second barbs being cut portions of the respective first and second side of the spring fastener.
 58. A vehicle as defined in claim 47, wherein the spring fastener further comprises an elastic body molded at least under the lower side of the head of the fastener.
 59. A vehicle as defined in claim 47, wherein the spring fastener further comprises: a casing surrounding at least partially the lower section of the U-shaped structure, except at least the free end of each spring, the casing enclosing the cavity within the first side and the second side of said U-shaped structure; and an elastic body comprised of at least a gasket, the gasket extending away from the closed cavity in the vicinity of the top of the U-shaped structure; wherein the casing is substantially non-elastic.
 60. A vehicle as defined in claim 47, wherein the fastener further comprising first barbs and second barbs being cut portions of the respective first and second side of the spring fastener.
 61. A vehicle as defined in claim 46, wherein the spring fastener further comprises a recess on at least one of: the first engagement spring and the second engagement spring.
 62. A vehicle as defined in claim 46, wherein the hindrance portion of the fastener further comprises one structure selected from ripple, side rib, upward solid bent extension parallel to the peak and the recess, knurled region, bent teeth, each having a depth, a bump, and a combination thereof.
 63. A vehicle as defined in claim 62, wherein the hindrance portion of the fastener further comprises a ripple in the vicinity of the peak.
 64. A vehicle as defined in claim 63, wherein the ripple comprises a back side with a curvature of a gradually decreasing slope.
 65. A vehicle as defined in claim 64, wherein the gradually decreasing slope has the shape of an arc in the range of 50–70 degrees with a radius in the range of 0.03–0.05 mm.
 66. A vehicle as defined in claim 46, wherein the fastener further comprising first barbs and second barbs being cut portions of the respective first and second side of the spring fastener.
 67. A vehicle as defined in claim 37, wherein the side-cuts of the at least one engagement spring have a triangular shape.
 68. A vehicle as defined in claim 37, wherein the lower edge of the side-cuts of the at least one engagement spring are at least partially bent outwardly.
 69. A vehicle as defined in claim 37, wherein the spring fastener further comprises a recess on at least one of: the first engagement spring and the second engagement spring.
 70. A vehicle as defined in claim 37, wherein the fastener further comprising first barbs and second barbs being cut portions of the respective first and second side of the spring fastener.
 71. A vehicle as defined in claim 37, wherein the spring fastener further comprises an elastic body molded at least under the lower side of the head of the fastener.
 72. A vehicle as defined in claim 37, wherein the spring fastener further comprises: a casing surrounding at least partially the lower section of the U-shaped structure, except at least the free end of each spring, the casing enclosing the cavity within the first side and the second side of said U-shaped structure; and an elastic body comprised of at least a gasket, the gasket extending away from the closed cavity in the vicinity of the top of the U-shaped structure; wherein the casing is substantially non-elastic.
 73. An assembly of a first part comprising a rib and a spring fastener, the spring fastener comprising a first side and a second side opposite the first side, the first side connected to the second side thereby forming a U-shaped structure having a cavity between the first side and the second side, a bottom portion wherein the first side and the second side are connected, and a top portion, the first side comprising a first engagement spring, the first engagement spring connected to the first side in the vicinity of the bottom portion, the second side comprising a second engagement spring, the second engagement spring connected to the second side in the vicinity of the bottom portion, each of the first and second engagement springs comprising a peak, a free end, and an engagement region between the peak and the free end, at least one engagement spring having two spring sides and a side-cut on each spring side, the side-cuts being across each other, thus forming a side-cut section aligned to be substantially parallel to the peak, each side-cut including an upper edge and a lower edge connecting with the respective spring side of the engagement spring, wherein the rib of the first part is inserted into the cavity of the spring fastener.
 74. An assembly as defined in claim 73, wherein the lower edge of the side-cuts of the at least one engagement spring are at least partially bent outwardly.
 75. An assembly as defined in claim 74, wherein the spring fastener further comprises an elastic body molded at least under the lower side of the head of the fastener.
 76. A vehicle as defined in claim 74, wherein the spring fastener further comprises: a casing surrounding at least partially the lower section of the U-shaped structure, except at least the free end of each spring, the casing enclosing the cavity within the first side and the second side of said U-shaped structure; and an elastic body comprised of at least a gasket, the gasket extending away from the closed cavity in the vicinity of the top of the U-shaped structure; wherein the casing is substantially non-elastic.
 77. An assembly as defined in claim 73, wherein the spring fastener further comprises an elastic body molded at least under the lower side of the head of the fastener.
 78. An assembly as defined in claim 73, wherein the spring fastener further comprises: a casing surrounding at least partially the lower section of the U-shaped structure, except at least the free end of each spring, the casing enclosing the cavity within the first side and the second side of said U-shaped structure; and an elastic body comprised of at least a gasket, the gasket extending away from the closed cavity in the vicinity of the top of the U-shaped structure; wherein the casing is substantially non-elastic.
 79. An assembly as defined in claim 73, wherein the spring fastener further comprises a hindrance portion within the engagement region, the hindrance portion comprising: a single-sided ripple with a back side in the vicinity of the peak; and inside substantially upper barbs on both first and second sides of the fastener.
 80. An assembly as defined in claim 79, wherein the back side of the single ripple has a gradually decreasing slope.
 81. An assembly of a second part comprising a slot and a spring fastener, the spring fastener comprising a first side and a second side opposite the first side, the first side connected to the second side thereby forming a U-shaped structure having a cavity between the first side and the second side, a bottom portion wherein the first side and the second side are connected, and a top portion, the first side comprising a first engagement spring, the first engagement spring connected to the first side in the vicinity of the bottom portion, the second side comprising a second engagement spring, the second engagement spring connected to the second side in the vicinity of the bottom portion, each of the first and second engagement springs comprising a peak, a free end, and an engagement region between the peak and the free end, at least one engagement spring having two spring sides and a side-cut on each spring side, the side-cuts being across each other, thus forming a side-cut section aligned to be substantially parallel to the peak, each side-cut including an upper edge and a lower edge connecting with the respective side of the engagement spring, wherein the spring fastener is disposed within the slot of the second part.
 82. An assembly as defined in claim 81, wherein the lower edge of the side-cuts of the at least one engagement spring are at least partially bent outwardly.
 83. An assembly as defined in claim 82, wherein the spring fastener further comprises an elastic body molded at least under the lower side of the head of the fastener.
 84. A vehicle as defined in claim 82, wherein the spring fastener further comprises: a casing surrounding at least partially the lower section of the U-shaped structure, except at least the free end of each spring, the casing enclosing the cavity within the first side and the second side of said U-shaped structure; and an elastic body comprised of at least a gasket, the gasket extending away from the closed cavity in the vicinity of the top of the U-shaped structure; wherein the casing is substantially non-elastic.
 85. An assembly as defined in claim 81, wherein the spring fastener further comprises an elastic body molded at least under the lower side of the head of the fastener.
 86. An assembly as defined in claim 81, wherein the spring fastener further comprises: a casing surrounding at least partially the lower section of the U-shaped structure, except at least the free end of each spring, the casing enclosing the cavity within the first side and the second side of said U-shaped structure; and an elastic body comprised of at least a gasket, the gasket extending away from the closed cavity in the vicinity of the top of the U-shaped structure; wherein the casing is substantially non-elastic.
 87. An assembly as defined in claim 81, wherein the spring fastener further comprises a hindrance portion within the engagement region, the hindrance portion comprising: a single-sided ripple with a back side in the vicinity of the peak; and inside substantially upper barbs on both first and second sides of the fastener.
 88. An assembly as defined in claim 87, wherein the back side of the single ripple has a gradually decreasing slope. 